(1) Field of the Invention
This invention relates to an apparatus for maintaining the bottom of a document in contact with the bottom of a document track while the document is fed bi-directionally within the track.
(2) Background Information
In certain document processing machines, like encoders and sorters, for processing documents, like checks and deposit slips, it is important to have the bottom of the document in contact with the bottom of a document track associated with the machine. Keeping the bottom of the document in contact with the bottom of the document track provides the registration necessary to have the document in registration with or aligned with certain document processing elements positioned along the length of the track in operative relationship therewith. Typical document processing elements are MICR readers and encoders or printers, for example.
Even though a document is positioned, initially, in proper registration with the document track (with the bottom length of the document in parallel contact with the bottom of the track), the document tends to become misaligned as it is moved in the track in operative relationship with the document processing elements positioned along the length of the track. This problem is solved in machines having unidirectional document transports by having the associated drive and/or idler rollers set at a fixed angle so as to provide a slight downward component of movement towards the bottom of the track as the document is moved along the length of the track.
The technique mentioned in the previous paragraph is not suitable when a bi-directional transport is used in the document processing machine. This is because the drive and/or idler rollers were set at a fixed angle to provide a downward component when the document is moved in only one direction. When the document is moved in the opposite direction in the document track, the drive and/or idler rollers raise the document away from the bottom of the document track. Providing a high-precision, parallel drive transport does not seem to work well at all times because "tolerance build-up" and dirt, for example, may result in unpredictable document skew.